cfq: Remove wait_request flag when idle time is being deleted

[safe/jmp/linux-2.6] / block / cfq-iosched.c

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f41fdb5..96f59ae 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2141,8 +2141,22 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
        /*
         * The active queue has run out of time, expire it and select new.
         */
-       if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
-               goto expire;
+       if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
+               /*
+                * If slice had not expired at the completion of last request
+                * we might not have turned on wait_busy flag. Don't expire
+                * the queue yet. Allow the group to get backlogged.
+                *
+                * The very fact that we have used the slice, that means we
+                * have been idling all along on this queue and it should be
+                * ok to wait for this request to complete.
+                */
+               if (cfqq->cfqg->nr_cfqq == 1 && cfqq->dispatched
+                   && cfq_should_idle(cfqd, cfqq))
+                       goto keep_queue;
+               else
+                       goto expire;
+       }
 
        /*
         * The active queue has requests and isn't expired, allow it to
@@ -3188,6 +3202,7 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                        if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
                            cfqd->busy_queues > 1) {
                                del_timer(&cfqd->idle_slice_timer);
+                               cfq_clear_cfqq_wait_request(cfqq);
                                __blk_run_queue(cfqd->queue);
                        } else
                                cfq_mark_cfqq_must_dispatch(cfqq);
@@ -3256,6 +3271,35 @@ static void cfq_update_hw_tag(struct cfq_data *cfqd)
                cfqd->hw_tag = 0;
 }
 
+static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+       struct cfq_io_context *cic = cfqd->active_cic;
+
+       /* If there are other queues in the group, don't wait */
+       if (cfqq->cfqg->nr_cfqq > 1)
+               return false;
+
+       if (cfq_slice_used(cfqq))
+               return true;
+
+       /* if slice left is less than think time, wait busy */
+       if (cic && sample_valid(cic->ttime_samples)
+           && (cfqq->slice_end - jiffies < cic->ttime_mean))
+               return true;
+
+       /*
+        * If think times is less than a jiffy than ttime_mean=0 and above
+        * will not be true. It might happen that slice has not expired yet
+        * but will expire soon (4-5 ns) during select_queue(). To cover the
+        * case where think time is less than a jiffy, mark the queue wait
+        * busy if only 1 jiffy is left in the slice.
+        */
+       if (cfqq->slice_end - jiffies == 1)
+               return true;
+
+       return false;
+}
+
 static void cfq_completed_request(struct request_queue *q, struct request *rq)
 {
        struct cfq_queue *cfqq = RQ_CFQQ(rq);
@@ -3295,11 +3339,10 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
                }
 
                /*
-                * If this queue consumed its slice and this is last queue
-                * in the group, wait for next request before we expire
-                * the queue
+                * Should we wait for next request to come in before we expire
+                * the queue.
                 */
-               if (cfq_slice_used(cfqq) && cfqq->cfqg->nr_cfqq == 1) {
+               if (cfq_should_wait_busy(cfqd, cfqq)) {
                        cfqq->slice_end = jiffies + cfqd->cfq_slice_idle;
                        cfq_mark_cfqq_wait_busy(cfqq);
                }
@@ -3717,6 +3760,10 @@ static void *cfq_init_queue(struct request_queue *q)
        cfqd->cfq_latency = 1;
        cfqd->cfq_group_isolation = 0;
        cfqd->hw_tag = -1;
+       /*
+        * we optimistically start assuming sync ops weren't delayed in last
+        * second, in order to have larger depth for async operations.
+        */
        cfqd->last_delayed_sync = jiffies - HZ;
        INIT_RCU_HEAD(&cfqd->rcu);
        return cfqd;